Researchers have discovered that a protein that is a major factor in the onset of Alzheimer's disease can also be found in the eyes of people with Down Syndrome. This link could allows doctors to test for Alzheimer's earlier.

A protein known as amyloid-beta has toxic properties that cause plaque to form in the brains of Alzheimer's patients, a major reason for the onset of the disease. Down syndrome sufferers have an extra copy of gene that regulates the protein, leading to even greater accumulation of amyloid-beta.

Lee Goldstein, an associate professor at Boston University School of Medicine and the Boston University Alzheimer's Disease Center and one of the co-leaders of the research team, explains the significance of this:

People with Down syndrome develop symptoms of Alzheimer's-type dementia often by the age of 30. This is because they have an extra copy of a key Alzheimer's gene that leads to increased amyloid-β accumulation in the brain. We discovered that this same protein starts to accumulate very early in the lens of the eye, even in children.

According to co-leader Julian Moncaster, the associate director of the Molecular Aging & Development Laboratory at Boston University, explains that the resultant cataracts that forms in the patients' eyes are telltale signs of future Alzheimer's:

The lens provides a window to the brain. The lens can't clear protein deposits the way the brain does. Our findings show that the same amyloid-beta protein that aggregates in the brain also accumulates in the lens and leads to these unusual cataracts in Down syndrome.

Part of the reason why this link hasn't been established earlier is perhaps because it's only relatively recently that people with Down syndrome are living long enough to be at risk of developing Alzheimer's. The life expectancy for Down syndrome patients was just 25 years as recently as 1983, although today it is up to 60. Now that this link has been discovered, Goldstein is optimistic that it can be used to identify at-risk patients at much earlier stages, setting up the opportunity for better treatment:

We are developing an eye scanner to measure amyloid-beta in the lens. This approach may provide a way for early detection and monitoring of related pathology in the brain. Effective treatments for the brain disease in Down syndrome and Alzheimer's disease are on the horizon, and early detection is the key for successful intervention.